Elastic supports of the above type are known to generally comprise a composite material base frame, a pad element made of a resilient material, usually expanded foam resin and/or gel, and a sheet cover element, which is designed to contact a seated user.
Typically, the frame of such supports is formed by in-mold hot curing of a thermosetting resin with one or more “skins” of fibrous material, such as carbon, fiberglass, Kevlar or the like embedded therein. The skins of fibrous material may be either dry or preimpregnated with the thermosetting resin when placed into the mold: in the former case, the thermosetting resin is directly injected into the mold.
When the cover element is formed of a polymer material due to aesthetic or light-weight requirements, a problem arises with the attachment of the composite material of the frame to the polymer material of the cover element.
International application PCT/IB2006/000144 discloses a composite material support structure comprising all the features as defined in the preamble of claim 1. In such prior art structure, the cover element is co-molded with the composite material frame, so that the cover element directly contacts the resin matrix of the composite material.
In practice, this solution has the drawback of imperfect adhesion between the frame and the cover element, which affects the mechanical properties of the finished support. The lack of affinity between the resin matrix of the frame and the polymer material of the cover element causes air bubble formation and discontinuity at the interface between the latter and the frame.
Thus, there still exists the problem of providing supports having a composite material frame attached to a cover element made of a polymer material, which exhibit good mechanical properties.
A further well-known problem of the above prior art support is that, when cuts or recesses are to be formed on the base frame, e.g. to create peripheral comfort tabs, according to the teaching of patent application WO2004031025, such processing has to occur upstream or downstream from the support molding process.
For upstream processing, the skins of fibrous material have to processed, wherefore cutting will be rough and inaccurate due to the nature of such material. On the other hand, downstream processing has to be carried out on the wholly formed frame, thereby causing such frame to be mechanically weakened.
In either case, the problem of forming a composite material support of high strength with high precision processing on the frame has not been solved to date.